The main idea for the first paragraph is that "Several people quickly found an article on the attack by the British Broadcasting Corp."
The main idea for the second paragraph is that "Many people feel that we react to terrible events differently on whom the victims are."
The main idea for the third paragraph is "People are more likely to care when terrible things happen to people and place to which they feel close."
The main idea for the fourth paragraph is " It is that closeness to Paris that made so many Americans express their sadness and shock on Facebook and Twitter."